/**
 * Licensed to the Apache Software Foundation (ASF) under one
 * or more contributor license agreements.  See the NOTICE file
 * distributed with this work for additional information
 * regarding copyright ownership.  The ASF licenses this file
 * to you under the Apache License, Version 2.0 (the
 * "License"); you may not use this file except in compliance
 * with the License.  You may obtain a copy of the License at
 *
 * http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */
package org.apache.hadoop.hbase.regionserver;

import java.io.IOException;
import java.util.Collection;
import java.util.Comparator;
import java.util.Iterator;
import java.util.List;
import java.util.Optional;
import java.util.stream.Collectors;

import org.apache.hadoop.conf.Configuration;
import org.apache.hadoop.hbase.Cell;
import org.apache.hadoop.hbase.CellComparator;
import org.apache.hadoop.hbase.KeyValue;
import org.apache.hadoop.hbase.regionserver.compactions.CompactionConfiguration;
import org.apache.yetus.audience.InterfaceAudience;
import org.slf4j.Logger;
import org.slf4j.LoggerFactory;
import org.apache.hbase.thirdparty.com.google.common.collect.ImmutableCollection;
import org.apache.hbase.thirdparty.com.google.common.collect.ImmutableList;
import org.apache.hbase.thirdparty.com.google.common.collect.Iterables;

/**
 * Default implementation of StoreFileManager. Not thread-safe.
 */
@InterfaceAudience.Private
class DefaultStoreFileManager implements StoreFileManager {
    private static final Logger LOG = LoggerFactory.getLogger(DefaultStoreFileManager.class);

    private final CellComparator cellComparator;
    private final CompactionConfiguration comConf;
    private final int blockingFileCount;
    private final Comparator<HStoreFile> storeFileComparator;
    /**
     * List of store files inside this store. This is an immutable list that
     * is atomically replaced when its contents change.
     */
    private volatile ImmutableList<HStoreFile> storefiles = ImmutableList.of();
    /**
     * List of compacted files inside this store that needs to be excluded in reads
     * because further new reads will be using only the newly created files out of compaction.
     * These compacted files will be deleted/cleared once all the existing readers on these
     * compacted files are done.
     */
    private volatile ImmutableList<HStoreFile> compactedfiles = ImmutableList.of();

    public DefaultStoreFileManager(CellComparator cellComparator, Comparator<HStoreFile> storeFileComparator, Configuration conf,
            CompactionConfiguration comConf) {
        this.cellComparator = cellComparator;
        this.storeFileComparator = storeFileComparator;
        this.comConf = comConf;
        this.blockingFileCount = conf.getInt(HStore.BLOCKING_STOREFILES_KEY, HStore.DEFAULT_BLOCKING_STOREFILE_COUNT);
    }

    @Override
    public void loadFiles(List<HStoreFile> storeFiles) {
        this.storefiles = ImmutableList.sortedCopyOf(storeFileComparator, storeFiles);
    }

    @Override
    public final Collection<HStoreFile> getStorefiles() {
        return storefiles;
    }

    @Override
    public Collection<HStoreFile> getCompactedfiles() {
        return compactedfiles;
    }

    @Override
    public void insertNewFiles(Collection<HStoreFile> sfs) throws IOException {
        this.storefiles = ImmutableList.sortedCopyOf(storeFileComparator, Iterables.concat(this.storefiles, sfs));
    }

    @Override
    public ImmutableCollection<HStoreFile> clearFiles() {
        ImmutableList<HStoreFile> result = storefiles;
        storefiles = ImmutableList.of();
        return result;
    }

    @Override
    public Collection<HStoreFile> clearCompactedFiles() {
        List<HStoreFile> result = compactedfiles;
        compactedfiles = ImmutableList.of();
        return result;
    }

    @Override
    public final int getStorefileCount() {
        return storefiles.size();
    }

    @Override
    public final int getCompactedFilesCount() {
        return compactedfiles.size();
    }

    @Override
    public void addCompactionResults(Collection<HStoreFile> newCompactedfiles, Collection<HStoreFile> results) {
        this.storefiles = ImmutableList
                .sortedCopyOf(storeFileComparator, Iterables.concat(Iterables.filter(storefiles, sf -> !newCompactedfiles.contains(sf)), results));
        // Mark the files as compactedAway once the storefiles and compactedfiles list is finalized
        // Let a background thread close the actual reader on these compacted files and also
        // ensure to evict the blocks from block cache so that they are no longer in cache
        newCompactedfiles.forEach(HStoreFile::markCompactedAway);
        this.compactedfiles = ImmutableList.sortedCopyOf(storeFileComparator, Iterables.concat(this.compactedfiles, newCompactedfiles));
    }

    @Override
    public void removeCompactedFiles(Collection<HStoreFile> removedCompactedfiles) throws IOException {
        this.compactedfiles = this.compactedfiles.stream().filter(sf -> !removedCompactedfiles.contains(sf)).sorted(storeFileComparator)
                .collect(ImmutableList.toImmutableList());
    }

    @Override
    public final Iterator<HStoreFile> getCandidateFilesForRowKeyBefore(KeyValue targetKey) {
        return this.storefiles.reverse().iterator();
    }

    @Override
    public Iterator<HStoreFile> updateCandidateFilesForRowKeyBefore(Iterator<HStoreFile> candidateFiles, KeyValue targetKey, Cell candidate) {
        // Default store has nothing useful to do here.
        // TODO: move this comment when implementing Level:
        // Level store can trim the list by range, removing all the files which cannot have
        // any useful candidates less than "candidate".
        return candidateFiles;
    }

    @Override
    public final Optional<byte[]> getSplitPoint() throws IOException {

        // TODO_MA 注释：
        return StoreUtils.getSplitPoint(storefiles, cellComparator);
    }

    @Override
    public final Collection<HStoreFile> getFilesForScan(byte[] startRow, boolean includeStartRow, byte[] stopRow, boolean includeStopRow) {
        // We cannot provide any useful input and already have the files sorted by seqNum.
        return getStorefiles();
    }

    @Override
    public int getStoreCompactionPriority() {
        int priority = blockingFileCount - storefiles.size();
        return (priority == HStore.PRIORITY_USER) ? priority + 1 : priority;
    }

    @Override
    public Collection<HStoreFile> getUnneededFiles(long maxTs, List<HStoreFile> filesCompacting) {
        ImmutableList<HStoreFile> files = storefiles;
        // 1) We can never get rid of the last file which has the maximum seqid.
        // 2) Files that are not the latest can't become one due to (1), so the rest are fair game.
        return files.stream().limit(Math.max(0, files.size() - 1)).filter(sf -> {
            long fileTs = sf.getReader().getMaxTimestamp();
            if(fileTs < maxTs && !filesCompacting.contains(sf)) {
                LOG.info("Found an expired store file {} whose maxTimestamp is {}, which is below {}", sf.getPath(), fileTs, maxTs);
                return true;
            } else {
                return false;
            }
        }).collect(Collectors.toList());
    }

    @Override
    public double getCompactionPressure() {
        int storefileCount = getStorefileCount();
        int minFilesToCompact = comConf.getMinFilesToCompact();
        if(storefileCount <= minFilesToCompact) {
            return 0.0;
        }
        return (double) (storefileCount - minFilesToCompact) / (blockingFileCount - minFilesToCompact);
    }

    @Override
    public Comparator<HStoreFile> getStoreFileComparator() {
        return storeFileComparator;
    }
}

